1. Field of the Invention
The invention pertains to the field of power management for electronic processing systems. More specifically, power usage is controlled on the basis of sensed feedback signals, such as voltage, current and temperature.
2. Discussion of the Related Art
Electronic systems designers are challenged by stringent and ever-changing requirements of new-generation processors. U.S. Pat. No. 6,414,469 issued to Zhou et al. describes these challenges as being a progressive drop in operating voltage from 5V to 3.3V towards an eventual range of from 1.1V to 0.8V. At the same time, current draws are increasing from about 13A to a range between 30A and 70A per processor. The tolerance for operational voltage is shrinking, e.g., from ±5% to ±1% of design voltage, while the processors are operating at ever higher frequencies and consuming more power. All of these factors combine to require more aggressive power management features than have previously been installed in electronic systems. The '469 patent addresses the problem of DC-DC converter noise by connecting voltage regulator modules in parallel such that, when a processor becomes active, the resultant transient response time of the converter is improved by transient ripples from the respective converters canceling one another. The '469 patent does not disclose a robust power management capability.
In general, robust power management features have not been incorporated into power converters or power supplies. U.S. Pat. No. 6,420,858 issued to Kitagawa et al. describes a DC-to-DC converter having a power saving mode. The '858 patent describes a variety of converters including converters with sense circuitry to monitor the voltage output. Sense signal feedback is used to control the voltage output of the converter at a level equal to a design power output. The use of sense circuitry that does not require a sense resistance may reduce power consumption in some designs. These features may save power, but they do not manage or control the delivery of power to a processor.
U.S. Pat. No. 4,276,591 issued to Quick describes a DC power supply that rectifies AC input power to produce a desired DC voltage. The DC power output is compared to a control signal to regulate the DC voltage through use of saturable reactors in the AC input lines. Thus, the system is capable of providing a constant output power at variable DC voltage and load current. While the power supply is useful in cathode sputtering systems and the like, the inability to control power output renders the power supply poorly suited for use in power management systems that require a varying power output.
Processor power management systems may include a programmable brownout detector, for example, as described in U.S. Pat. No. 6,304,823 issued to Smit et al. The brownout detector is designed to sense an under-voltage condition below a minimum operating threshold for the processor. The minimum operating threshold may be supplied as a programmable value. The '823 patent, however, does not describe a power management system in which the brownout control may conflict with other power management objectives.